Can Anyone Prevent Trump From Ordering A Nuclear Strike? Not Really.

This extraordinary executive power has been contested throughout American history.

It's 2 a.m. President Donald Trump awakes to an alert on his phone. It's another taunt from North Korean dictator Kim Jong Un, the latest in an escalating row of provocations. But Kim's gone too far this time. A retaliatory tweet just won't cut it.

Enraged, Trump races to his desk and slams his fist on the "nuclear button." World War III begins.

Could this catastrophic scenario become a reality?

At a time when such a dramatic question may actually feel pertinent, one can find solace in the answer: No (well, not exactly). Firstly, Trump's "nuclear button" doesn't exist, despite his recent claim that it's "bigger & more powerful" than Kim's. But the president does have access to the nuclear codes, as well as the sole authority to order a strike.

This extraordinary executive power has been contested throughout American history. When North Korea shot down a U.S. spy plane in 1969, a drunken President Richard Nixon reportedly "became incensed and ordered a tactical nuclear strike," according to CIA official George Carver. "The Joint Chiefs were alerted and asked to recommend targets, but [Secretary of State Henry Kissinger] got on the phone to them. They agreed not to do anything until Nixon sobered up in the morning."

Efforts to rein in the president's nuclear powers are still underway today, with Trump repeatedly threatening to "totally destroy" North Korea, a nation of 25 million people. Sen. Edward Markey (D-Mass.) and Rep. Ted Lieu (D-Calif.) introduced legislation last year that would prohibit the president from launching a nuclear first strike before Congress declares war.

So now, with Trump at the helm, how would the situation actually unfold? HuffPost spoke with six experts about the extent and limits of the president's nuclear authority. Many agreed that radical checks and balances to this power are long overdue.

What's the step-by-step procedure in the U.S., and how does it differ for first nuclear strike versus a retaliatory launch?

Stephen Schwartz, independent nuclear policy consultant: There are different scenarios. There's the one where we are under attack, and then there's the scenario that people talk about (which is probably less likely) where Trump is watching Fox News, or sitting on the toilet or whatever, and decides "the hell with Kim Jong Un, I'm gonna take him out" and decides to initiate a nuclear strike.

In the first situation, our early-warning radars and satellites would receive indication of a ballistic missile attack against the United States, and officials at [the North American Aerospace Defense Command] would assess that information. Assuming that it is a real threat, there would be a conference to loop the president in. He could involve any number of officials, and can then decide to either do nothing, or to launch some of our nuclear weapons out from under the incoming attack before it hits, or he can decide to launch everything.

The president is accompanied at all times by a military aide with a briefcase known as the "nuclear football." In that briefcase are the means enabling him to order the use of nuclear weapons, if he so chooses. Because of the enormous time pressures, he might have as little as five minutes to make a decision.

The only thing that could stop a president who's determined to use nuclear weapons is mass insubordination. Stephen Schwartz, independent nuclear policy consultant

The president would then retrieve from his pocket a laminated card nicknamed the "biscuit," which contains alphanumeric challenge codes which he would use to identify himself to the director of operations in the "war room" at the Pentagon. Once his identity is verified, he gives the order and it is transmitted down the chain of command. The chain of command goes from the president through the chairman of the Joint Chiefs of Staff, and then, if we're using long-range weapons, down through the Strategic Command, then the order is relayed to our forces in the field. It always happens extremely quickly.

Then there's the abnormal scenario, where the president decides for no particular reason at all that he wants to use nuclear weapons. He could involve other people, but he doesn't have to. Even if other people are involved in the discussion, at the end of the day they have no legal power. They can object all they want, and the president's order still goes through. If somebody were to refuse to carry out the order, the president could fire that person or direct the secretary of defense to fire him.

It's important to note that the president doesn't have the ability to launch nuclear weapons on his own. He can authorize nuclear weapons to be used, but he doesn't physically control them. He needs help, but the system is predicated on all this happening extremely fast, with nobody questioning it. If it's a valid order, [operators] will go ahead and launch the weapons. They're not really trained to think; they're trained to push button and pull triggers.

Carlos Barria / ReutersDefense Secretary James Mattis listens to remarks by Trump on Jan. 27. If someone refused to carry out a nuclear launch order, the president could direct the secretary of defense to fire that person.

Under what circumstances would it be legal for Trump to order an attack?

Lisbeth Gronlund, senior scientist and co-director of the Global Security Program at the Union of Concerned Scientists: There are three basic criteria for the lawfulness of the use of any military weapons: the first is military necessity, which means an attack has to be limited to military objectives; distinction, which means the attack must be able to discriminate between military and civilian targets; and proportionality, which means the military objective has to outweigh the harm to civilians.

Bruce Blair, nuclear security expert and research scholar at the Program on Science and Global Security at Princeton University: There are two different questions. One is strictly legal, and the other is whether the chain of command would treat it as a legal one. I think for all intents and purposes, the chain of command would obey an order to carry out a nuclear strike, unless that strike is obviously illegal. I think that's a very high bar.

I think senior military commanders broadly defer to the president to determine when and how nuclear weapons would be used in the defense of the United States and that they would defer to [Trump's] judgment. If this nuclear crisis with North Korea continues to escalate and Trump decides to order a nuclear strike against North Korea, I think it would be considered legal by the chain of command.

Beatrice Fihn, executive director of the International Campaign to Abolish Nuclear Weapons: It's a complex question, because we [at ICANW] would consider any use of nuclear weapons to be illegal, given the casualties it would cause. It would violate the Geneva Convention in laws of war in many different ways; both the disproportionate response, for example, and that you're not supposed to target civilians in warfare, whereas nuclear weapons are created to kill as many civilians as possible. They're not really made for precision guidance military targets. They're meant to wipe out cities. It would also violate environmental law, given the huge environmental impacts that nuclear weapons have.

I'm sure there are other lawyers who would argue differently and could see a hypothetical scenario that wouldn't have those kind of consequences. But if we're talking about North Korea, I don't see anyone being able to claim that a use of nuclear weapons would be in line with international humanitarian laws and the laws of war that we have agreed on.

Can you envision a scenario in which Trump might order a first-use strike?

Blair: I think if President Trump comes to the conclusion that a nuclear strike against the United States is imminent, he would seriously consider launching our conventional forces to try to pre-emptively destroy this looming threat. The context may be one in which Trump and Kim Jong Un have escalated their brinkmanship to the point of conflict, and Kim may have fled to his wartime bunker.

But yes, I can [envision such a scenario]. I think the Korean crisis has already crossed the threshold into a danger zone that is quite threatening and that could trigger either side to employ force ― presumably conventional forces first, but that which could then escalate to the use of nuclear weapons.

No person is sane enough, stable enough or good enough to have the ability to end the world. Beatrice Fihn, executive director of the International Campaign to Abolish Nuclear Weapons

Schwartz: It's hard to say. Donald Trump has been talking about nuclear weapons for a very long time. He has a very high opinion of himself on this, as with all other matters, and thinks he knows everything. I frankly can't think of a more dangerous combination in a president than somebody who is so reckless with his words and knows so little about what these weapons actually do ― and doesn't want to learn any more about how destructive this would be.

He said throughout the campaign that he didn't want to take anything off the table, including using nuclear weapons. I don't know, and that's really the problem here: We don't have a good sense of what the president would or wouldn't do. There are cooler heads around the president who would presumably caution him to be more cautious, but if they've been doing that for the past year, it doesn't seem to have had any effect. There seems to be an attitude within the White House of "Let Trump be Trump."

I worry less about the president suddenly deciding to use nuclear weapons and more about him boxing himself into a corner through his tweets, statements and attitude that nobody is better than he is. I worry that he walks into a situation where he thinks he's being smart, then blunders himself into a corner where the only recourse to get out without looking like an idiot is to use nuclear weapons or go to war, or precipitate a war.

Scott Sagan, professor of political science at Stanford University and senior fellow at Stanford's Center for International Security and Cooperation: A preemptive strike: If Trump received intelligence that the North Koreans were fueling a large number of their liquid-fueled missiles and believed that a North Korean attack was likely, he could order a preemptive strike using U.S. [intercontinental ballistic missiles] against the launch sites, missile storage sites, and North Korean command and control facilities. This would be legal under the doctrine of anticipatory self-defense.

However, If Trump declared in that scenario (or in any other scenario) that he wanted to "totally destroy" Pyongyang and ordered [U.S. Strategic Command] to aim at the center of the city, such an order would be illegal. This might sound like a far-fetched idea, but recall that Trump said at the U.N. in September that if the U.S. "is forced to defend itself or its allies, we will have no choice but to totally destroy North Korea." I would hope that either Secretary of Defense James Mattis or STRATCOM Commander Gen. John Hyten would tell him that this was an illegal order and that they would not obey it.

What do you think of the Lieu-Markey bill, which would require congressional approval for a nuclear strike?

Peter Feaver, political science professor at Duke University and former special adviser on the National Security Council, who testified at a Senate Foreign Relations Committee hearing in November about the president's nuclear authority: I think it's high time that we took a close look at our nuclear command and control system to include aspects of how the decision would be made by the president and his advisory team, and how it would be transferred down, and what kinds of safety measure you might build in to ensure that decision is not made hastily or in error.

Reviewing and hardening [this system] to make it more robust and resilient is wise and needs to be done. That may not be effectively done by legislation imposed by Congress. My concern, and what I told the senators, is that if you tried to foist something on the executive branch by passing legislation ― first of all, it's unlikely it would pass, and second of all, it's unlikely the president would sign it ― it's unlikely that it would play out in practice the way the legislative designers intended.

Blair: It's a step in the right direction. Assuming that Congress would declare war and provide the specific authorization for the use of nuclear weapons, it still would not be an airtight safeguard because the president can still make a very ill-advised decision sometime down the road, in the midst of some conflict. Also, there could be situations when a threat is so imminent that there simply would not be time to debate and produce a declaration of war. So it has some weaknesses.

I think an additional, invaluable congressional solution would be for Congress to pass a law prohibiting the first use of nuclear weapons. If they could pass such a law, which is very unlikely given the complexion of the Congress in the control of the Republican Party, it would lay out clear markers and red lines that the president could not exceed. If he did, he would be held accountable and even impeachable.

Do you have any concerns about the current process and/or extent of the president's authority? What changes do you recommend, if any?

Schwartz: Having some sort of screening process [for the president] would be good. Having at least one other person in the decision-making loop who has to positively affirm not just the president's identity but has to also agree that the decision would not be a bad thing. We are one of the only nuclear-armed countries in the world that vests this power in one person. It could be the secretary of state, it could be the secretary of defense, it could be a member of Congress in the presidential line of succession. But when you're talking about something that could literally end the world, it should not be the sole responsibility of one person ― particularly one person who is so temperamentally challenged and mercurial.

Fihn: It's terrifying to think that one person in each of the nuclear-armed states has this authority to launch nuclear weapons, to launch a weapon of mass destruction on civilians. At the same time, I think any use of these weapons would violate the laws of war, which means that even use with many people's authorizations would be wrong and immoral. Of course, it's deeply disturbing that it's so easy for a president to launch weapons and that there's very little people around him could do, but nuclear weapons are an ongoing threat, no matter who has control of them. Any use would cause a catastrophic humanitarian situation. First- or second-strike isn't really where the discussion needs to be. The discussion needs to be: Is it OK to use WMD?

With [Trump's] tweet, it's worrying to see such language. But he's just expressing what nuclear weapons are. Nuclear weapons are meant to indiscriminately kill as many people as possible. All nuclear-armed states have policies that say they are ready to do this to people, right now. Many people are very worried now with Donald Trump having access to these weapons, but if you have a problem with Trump having the weapons, it's probably the weapons themselves that are the problem. No person is sane enough, stable enough or good enough to have the ability to end the world.

The above interviews have been edited and condensed for clarity.

SAUL LOEB/AFP via Getty ImagesThe war of words between U.S. President Donald Trump and North Korean leader Kim Jong Un is rapidly escalating.